In addition to functionality, in the present day and age, the outer and inner appearance of the motor vehicle plays an increasingly more important role. In addition to upscale decors, equipment parts are increasingly provided with light guides and light sources that illuminate the equipment part. Injection-molded planar light guides, for example, are frequently used on equipment parts. Light is coupled into the light guide outside a visible area and is coupled out across the entire surface area of the light guide in the visible range.
To achieve homogeneous outcoupling of the light across the entire surface area of the light guide, the surface of the light guide is usually roughened. The rough surface introduces irregularities into the light guide, which scatter the incoupled light and therefore favor light outcoupling. The roughened surface is usually generated by mechanical processing, such as grinding or embossing. Such methods, however, may have the disadvantage that the light guide must be sufficiently thick because otherwise there is the risk that the light guide becomes damaged, or even destroyed, due to insufficient inherent rigidity. This can drastically limit the use of light guides on equipment parts, because the equipment parts must always be adapted to the wall thicknesses of the light guides.
Moreover, the light guide may be required to be adapted to the shape of the equipment part. Using the light guide on other equipment parts may only be possible in certain cases. This can have an adverse effect on the production costs, in particular in the case of injection-molded light guides, because a separate mold may need to be kept available for each light guide shape.
While it is also possible to dispose light guides beneath the visible side of an equipment part, which creates degrees of freedom with respect to the shape of the light guide, this arrangement may also have drawbacks. For example, the layer forming the visible side may be weakened or thinned in the region of the light guide, so that the light guide is able to trans-illuminate it. Equipment parts, however, frequently include attachment elements outside the visible range, via which the equipment part can be attached to the vehicle. However, these attachment parts may limit the arrangement options of the light guide. In addition, sufficient installation space may be required to be able to integrate the light guide.